The present invention concerns electronic flash attachments for photographic cameras, of the type which are mounted on a camera's flash-attachment mount, the mounting of the attachment on the mount effecting electrical connections between circuitry internal to the flash attachment and circuitry internal to the camera.
Electronic flash attachments are used, of course, to illuminate the scene which a camera is to photograph. The flash attachment is typically electrically connected to the camera to assure correct operation, e.g. to synchronize the emission of flashed light with the opening of the camera's shutter.
With conventional flash attachments, the connector employed is typically a mounting shoe permanently mounted on the camera housing, the flash attachment having a mounting foot which slides into the mounting shoe and furthermore establishes electrical connections between contacts of the mounting foot and shoe. Such a connecting action permits a two-pole electrical connection, implemented via a so-called ground contact and a synchronization contact of the camera. Such mounting feet and mounting shoes are highly standardized, so that an electronic flash attachment having such a mounting foot can be used in cooperation with any camera having a standardized mounting shoe.
However, over the years, cameras have been developed whose cooperation with their associated flash attachments go beyond the mere use of a synchronization contact. For example, in some camera plus flash-attachment systems, there is provided in the camera viewfinder a visible indication of whether the flash unit is or is not in readiness to perform a flash. In other systems, the flash unit automatically transmits to the camera a signal informing a control circuit that the camera shutter speed is to be adjusted in correspondence to flash operation. In further such systems, the camera's internal exposure-duration control system furnishes a signal to the flash attachment, commanding flash termination. Such additional instances of cooperation between the camera and the flash attachment of course make necessary the provision of implementing circuitry both internally of the camera and internally of the flash attachment, as well as means for connecting together such camera and flash-attachment circuitry.
These differing versions of additional cooperation between camera and flash attachment are different in different camera plus flash-attachment systems, with the result that a special electronic flash attachment is required for each different system and can only be used with the camera of that system.